The HEAT repeat protein Blm10 regulates the yeast proteasome by capping the core particle

Marion Schmidt, Wilhelm Haas, Bernat Crosas, Patricia G. Santamaria, Steven P. Gygi, Thomas Walz, Daniel Finley

Research output: Contribution to journalArticlepeer-review

155 Scopus citations


Proteasome activity is fine-tuned by associating the proteolytic core particle (CP) with stimulatory and inhibitory complexes. Although several mammalian regulatory complexes are known, knowledge of yeast proteasome regulators is limited to the 19-subunit regulatory particle (RP), which confers ubiquitin-dependence on proteasomes. Here we describe an alternative proteasome activator from Saccharomyces cerevisiae, Blm10. Synthetic interactions between blm10Δ and other mutations that impair proteasome function show that Blm10 functions together with proteasomes in vivo. This large, internally repetitive protein is found predominantly within hybrid Blm10-CP-RP complexes, representing a distinct pool of mature proteasomes. EM studies show that Blm10 has a highly elongated, curved structure. The near-circular profile of Blm10 adapts it to the end of the CP cylinder, where it is properly positioned to activate the CP by opening the axial channel into its proteolytic chamber.

Original languageEnglish (US)
Pages (from-to)294-303
Number of pages10
JournalNature Structural and Molecular Biology
Issue number4
StatePublished - 2005
Externally publishedYes

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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